Radially yielding cylinder and piston arrangement

ABSTRACT

A piston structure, located in a cylinder to which pressure fluid can be supplied, includes a piston rod with a rigidly secured support piston on which a sealing piston, sliding in the cylinder, is mounted with radial play. The support piston is spaced from the cylinder surface and can move radially relative to the sealing piston and to the cylinder surface when the piston rod is radially displaced. Preferably, pressure areas balance the sealing piston in axial direction so that friction is reduced during relative radial movement between the support piston and the sealing piston due to radial displacement of the piston rod.

United States Patent Sandau Jan. 15, 1974 [54] RADIALLY YIELDINGCYLINDER AND 1,988,726 1/1935 Godron 277/27 PISTON ARRANGEMENT 2,068,859l/l937 Jones et al. 92/258 2,460,948 2/1949 Sander 92/258 Inventor:Hartmut g g 3,207,426 9/1965 Gassmann et al.. 277/27 Germany v 3,247,7674/1966 Aslan 92/258 X [73] Assignee: Robert Bosch GmbH, Stuttgart,Primary Examiner lrwin 0 Cohen Germany Att0rney-Michael S. Striker [22]Filed: Jan. 14, 1972 21 Appl. No.: 217,920 1 ABSTQACT A pistonstructure, located in a cylinder to WhlCh pres sure fluid can besupplied, includes a piston rod with a Foreign Application Priority Datarigidly secured support piston on which a sealing pis- Jan. 27, 1971Germany P 2103 646.4 ton, sliding in the cylinder, is mounted withradial play. The support piston is spaced from the cylinder [52] U.S. Cl92/181, 92/244, 92/258 surface and can move radially relative to thesealing [5 1] Int. Cl. Fl6j 1/00, F16j 9/00 piston and to the cylindersurface when the piston rod [58] Field of Search 92/181, 182, 184, isradially displaced. Preferably, pressure areas bal- 92/244, 251, 257,258; 277/27, 70 ance the sealing piston in axial direction so thatfriction is reduced during relative radial movement be- [56} ReferencesCited tween the support piston and the sealing piston due to UNITEDSTATES PATENTS radial displacement of the piston rod.

680,465 8/1901 Reynolds 92/258 5 Claims, 3 Drawing Figures PATENIED JAN1 5 I974 SHEET 1 0f 2 Fig.1

1 RADIALLY YIELDING CYLINDER AND PISTON ARRANGEMENT BACKGROUND OF THEINVENTION DESCRIPTION OF THE PREFERRED EMBODIMENTS In the tubularcylinder 1 ofa working cylinder means,

The present invention relates to a cylinder and piston a pistonstructure 2 is movable in axial direction, and

arrangement in which the piston structure includes a piston rod, and apiston means composed of several parts.

An arrangement of this type is disclosed in the U. S. Pat. No. 2,371,553which has the disadvantage that the sealing piston with its sealingrings, is rigidly secured to the piston rod. In the event that thepiston rod deviates even slightly from its correct position located inthe axis of the cylinder, the sealing rings are compressed to compensatethe relative displacement between the sealing piston and the cylindersurface. Such an arrangement requires a wide radial spacing of thepiston means from the cylinder surface in order to prevent binding ofthe piston. The device may cause uneven pressures on the sealing rings,resulting in increased wear so that the sealing rings require serviceand exchange.

SUMMARY OF THE INVENTION It is one object of the invention to overcomethe disadvantages of known cylinder and piston arrangements, and toprovide a radially yielding piston arrangement which reliably operatesand consists of sim ple parts which can be inexpensively manufactured.

Another object of the invention is to provide a sup port piston which isradially movable with the piston rod without engaging the cylindersurface, and a sealing piston mounted with play on the support pistonand sliding on the cylinder surface.

With these objects in view, the piston rod means of the invention ismovable relative to a sealing piston in radial direction.

A cylinder and piston arrangement according to a preferred embodiment ofthe invention comprises a piston structure including a piston rod meanslocated in a cylinder spaced from the inner surface of the same, andsealing piston means located in the cylinder means in sealing andsliding contact with the cylinder surface, and being mounted on thepiston rod means for axial movement therewith, and radially spacedtherefrom.

Consequently, the piston rod means, which preferably BRIEF DESCRIPTIONOF THE DRAWING FIG. 1 is an axial sectional view illustrating a cylinderand piston arrangement according to one embodiment of the invention;

FIG. 2 is an axial sectional view illustrating a simplified modificationof the embodiment of FIG. 1; and

FIG. 3 is an axial sectional view illustrating another embodiment of theinvention.

may be operated by admitting pressure fluid to the chambers formed bythe piston structure 2 in the cylinder means 1.

The piston structure 2 consists of several parts, including a piston rod3 to which two disks 4 and 5 and an intermediate sleeve 6 are secured bya nut 7 on a threaded end portion of piston rod 3, nut 7 pressing thesupport piston 4, 5, 6 against a shoulder formed on piston rod 3. Thesupport piston 4, 5,. 6 is rigidly secured to piston rod 3 and moveswith the piston rod in axial direction, and also in radial directionswhen piston rod 3 is displaced out of a central position in which itsaxis coincides with the axis of the cylinder surface 14, in whichposition the piston rod 3 is held by a bearing in an end member of thecylinder 1.

The peripheral rims of the disks -4 and 5 are radially spaced bycircular gaps from the inner cylinder surface 14 so that a small radialdisplacement of piston rod 3 with disks 4 and 5 will not causeengagement of the peripheral rims of the disks 4 and 5 with the innercylinder surface 14.

Between disks 4 and 5 of the support piston, an annular sealing piston 9is mounted with ample axial play, and also surrounding the sleeve 6 withample radial play. The sealing piston 9 has two sealing rings 10 and I1surrounding its outer peripheral surface, and having lips opening inopposite directions toward the chambers which are located in oppositesides of the piston means in cylinder 2. Between the two sealing rings10 and 11, a guide ring 13 surrounds the sealing piston 9 in a centrallocation. Sealing rings 10 and l l, and guide ring 13 are in sliding andsealing contact with the inner cylinder surface 14, as required foraxial movement of the piston structure 2 when pressure fluid is admittedto a pressure chamber on one side of the piston structure 2.

The confronting inner planar surfaces 15 and 16 of disks 4 and 5 areformed with circular grooves in which two sealing rings 17, 18 and 19,20, respectively are mounted spaced from each other in radial direction,respectively, which are in sealing contact with lateral end faces of thesealing piston 9, and form on the same annular pressure areas 21 and 22,respectively. Each pressure area 21 and 22 is connected by a conduit 23and 24, respectively, in the sealing piston 9 with the interior of thecylinder 1 by ports in sealing piston 9 located adjacent the disks 4 and5, respectively. At the points where the ports of conduits 23 and 24open, the distance between the clearing piston 9 and the inner cylindersurface 14 is substantial in radial direction.

FIG. 1 shows several lines provided with arrows to indicate diametricaldistances and diameters. The diameter d is equal to the diameters d;,,which are the diameters of the outer sealing rings 19 and 17. The diameter d, is equal to the diameters d which is the diameter of the sealingrings 18 and 20. The diameter d is equal to the diameter of the innercylinder surface 14. Assuming that pressure fluid has been introduced onthe right side of piston structure 2 into cylinder 1, the disk 5 isunder fluid pressure on an effective surface which is circular and hasthe diameter d since the fluid pressure also acts on the opposite sideof disk 5 on the effective annular surface having the inner diameter dThe respective force is directly transmitted from disk to piston rod 3to which disk 5 is rigidly secured by nut 7.

The force which acts on an annular surface on the right end face ofsealing piston 9 having the diameter d, on the outside and the diameterd, on the inside, is compensated by the force produced by the pressurein the pressure area 21, which is connected by conduit 23 with the highpressure chamber of cylinder 1. Consequently, the sealing piston 9 isfree of pressure and balanced, and has to overcome only the friction onthe annular sealing rings 17 to 20 when the piston structure 2 makes aradial movement due to a radial movement of piston rod 3 deviating fromits neutral correct postion in which its axis coincides with the axis ofthe cylinder surface 14. Without the pressure relief conduits 33, 24 andthe annular pressure areas 22, 21, the sealing piston 9 may not move inradial direction relative to the support piston 4, 5, 6, and to thecylinder surface 2, since the friction forces could be too great. Whenthe piston structure 2 is moved in the other direction, correspondingpressure conditions take place, and the pressure equilibrium is obtainedby the conduit 24 through which the pressure fluid flows into thepressure area 22.

In the embodiment of FIG. 2, the support piston 4', 5', 6, is secured tothe piston rod 3 as shown in FIG. 1, and a sealing piston 9 is mountedsurrounding sleeve 6' and located between the disks 4 and 5. The innercircular surface of sealing piston 9' is spaced by a radial gap from theouter cylindrical surface of sleeve 6, and also spaced in axialdirection from the confronting lateral surfaces of the disks 4 and 5. Asealing ring 19' is provided only on one side of the sealing piston 9'in a circular groove in the lateral surface of disk 5'.

The axial pressure which does not act on disk 5, is not compensated, asin the embodiment of FIG. 1, but if the diameter d is great, thedifference in the function ofthe devices shown in FIGS. 1 and 2 issmall. The simplified construction of FIG. 2 eliminates the axialconduits 23, 24, the smaller sealing ring 20, and both sealing rings 17and 18. I

In the embodiment illustrated in FIG. 3, the support piston includes, inaddition to the outer disks 27 and 28, also a central disk 29 which isequidistant from the outer disks 27 and 28. The three disks are spacedby circular sleeves 36 and 37, and all parts 27, 36, 29, 37, 28 arepressed against the annular shoulder 8 by nut 38.

Between disks 27 and 29, and also between disks 29 and 28, two sealingpistons 30 and 31, having angular cross-sections,are arrangedsurrounding the sleeves 36 and 37, and being surrounded by sealing rings32 and 33 provided with outwardly opening lips. The confronting innerlateral surfaces of the sealing pistons 30 and 31 hold, in correspondingcircular grooves, sealing rings 34 and 35. Sealing pistons 30 and 31have ample radial play about the spacing sleeve 36 and 37, and alsoaxial play in relation to the disks 27, 28, 29. Annular gaps 39 and 40are located between the sealing pistons 30, 31 and the sleeves 36, 37.Openings or bores 41, 42 in disks 27 and 28, respectively, connect theannular gaps 39 and 40, respectively, with the respective correlatedpressure chamber in the cylinder.

The outer diameter of the sealing rings 34, 35 is designated a, and theinner diameter of the cylinder 1 is designated D. Due to the pressure inthe annular gaps 39, 40, a pressure area 44, 43, respectively, is builtup, the pressure areas being limited by sealing rings 34 or 35.

Assuming that the pressure chamber in cylinder 1 on the right side ofthe piston structure 2 is filled with pressure fluid, the sealing piston31 is balanced and the pressure relieved by the pressure area 43 whichreceives pressure fluid through the annular gap 40 and opening 42 indisk 28. Only a small force remains which is caused by the annularsurface having the outer diameter D and the inner diameter d, and actingon the central disk 29, which is also rigidly secured to the piston rod3 so that this small force is also transmitted in axial direction to thepiston rod 3.

The force produced by the pressure on the surface having the diameter dacting on the piston means, is partly taken up by disk 29, due to thepressure area 42, and partly directly transmitted to the piston rod 3'.Only a small force is required for displacing the sealing pistons 30, 31in radial direction when thepiston rod 3 is radially displaced, sincethe sealing pistons 30 and 31 are balanced, and the friction between thesame and the disks 27, 28, 29 is reduced.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofcylinder and piston arrangements differing from the types describedabove.

While the invention has been illustrated and described as embodied in aradially yielding cylinder and piston arrangement having a supportpiston on which a sealing piston is mounted with radial play, andpreferably balanced in axial direction, it is not intended to be limitedto the details shown, since various modifications and structural changesmay be made without departing in any way from the spirit of the presentinvention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

I claim:

1. Radially yielding cylinder and piston arrangement, comprising acylinder means having an inner surface; a piston rod; support pistonmeans secured to said piston rod and located in said cylinder means,said support piston means including axially spaced disks havingperipheral rims radially spaced from said inner surface; an annularsealing piston means surrounding with play the portion of said supportpiston means located between said disks and having lateral facesconfronting said disks; plural sealing means between said lateral facesand said disks forming separate pressure areas, said sealing pistonmeans having separate ducts connecting the pressure area adjacent eachof said disks with the interior of said cylinder means adjacent therespective other disk so that said sealing piston means is balancedbetween said disks and relieved of axial pressure, said sealing pistonmeans being spaced from said inner surface and having at least oneperipheral recess; and annular sealing ring means in said recess havingan outer surface in sliding contact with said inner surface so that saidsupport piston means can radially move relative to said balanced sealingpiston means and to said annular sealing ring means when said piston rodmoves in radial direction.

2. An arrangement as claimed in claim 1, wherein said sealing meansbetween said lateral faces and said disks include two concentric sealingrings on each disk, forming annular pressure areas, each annularpressure area being connected by the respective duct with a peripheralportion of said sealing piston means spaced from said inner surface.

3. An arrangement as claimed in claim 1 wherein said support pistonmeans includes sleeve means surrounding a piston rod portion betweensaid two disks, and being surrounded by said sealing piston means withradial play.

4. An arrangement as claimed in claim 1 wherein said sealing pistonmeans includes a sealing piston, a central guide ring surrounding saidsealing piston and sliding on said inner surface, and two axially spacedyieldable sealing rings on opposite sides of said guide ring sliding onsaid inner surface, and having sealing lips engaging said sealing pistonmeans and said inner surface, respectively.

5. An arrangement as claimed in claim 1 wherein said piston rod has anannular shoulder and a threaded end portion, said support piston meansmounting said sealing piston means and including sleeve meanssurrounding said piston rod, and nut means engaging said threaded endportion and pressing one of said disks against said shoulder so thatsaid] sleeve means and disks of said support piston means are rigidlysecured to said piston means.

1. Radially yielding cylinder and piston arrangement, comprising acylinder means having an inner surface; a piston rod; support pistonmeans secured to said piston rod and located in said cylinder means,said support piston means including axially spaced disks havingperipheral rims radially spaced from said inner surface; an annularsealing piston means surrounding with play the portion of said supportpiston means located between said disks and having lateral facesconfronting said disks; plural sealing means between said lateral facesand said disks forming separate pressure areas, said sealing pistonmeans having separate ducts connecting the pressure area adjacent eachof said disks with the interior of said cylinder means adjacent therespective other disk so that said sealing piston means is balancedbetween said disks and relieved of axial pressure, said sealing pistonmeans being spaced from said inner surface and having at least oneperipheral recess; and annular sealing ring means in said recess havingan outer surface in sliding contact with said inner surface so that saidsupport piston means can radially move relative to said balanced sealingpiston means and to said annular sealing ring means when said piston rodmoves in radial direction.
 2. An arrangement as claimed in claim 1,wherein said sealing means between said lateral faces and said disksinclude two concentric sealing rings on each disk, forming annularpressure areas, each annular pressure area being connected by therespective duct with a peripheral portion of said sealing piston meansspaced from said inner surface.
 3. An arrangement as claimed in claim 1wherein said support piston means includes sleeve means surrounding apiston rod portion between said two disks, and being surrounded by saidsealing piston means with radial play.
 4. An arrangement as claimed inclaim 1 wherein said sealing piston means includes a sealing piston, acentral guide ring surrounding said sealing piston and sliding on saidinner surface, and two axially spaced yieldable sealinG rings onopposite sides of said guide ring sliding on said inner surface, andhaving sealing lips engaging said sealing piston means and said innersurface, respectively.
 5. An arrangement as claimed in claim 1 whereinsaid piston rod has an annular shoulder and a threaded end portion, saidsupport piston means mounting said sealing piston means and includingsleeve means surrounding said piston rod, and nut means engaging saidthreaded end portion and pressing one of said disks against saidshoulder so that said sleeve means and disks of said support pistonmeans are rigidly secured to said piston means.